Victor's issue was slightly different, so here is the (very ambiguous) error message that I saw. I'm including it here to make it easy to search with Google, and so that I can find this in the future:
Event Type: Error
Event Source: BizTalk Server 2006
Event Category: BizTalk Server 2006
Event ID: 5753
Time: 5:00:37 PM
A message received by adapter "FILE" on receive location "Rloc_Recs_FF"
with URI "C:\acme-inbound\ACME_CT\Inbound Flat File\*.*" is suspended.
Error details: The system cannot find the file specified. (Exception from HRESULT:
For more information, see Help and Support Center at http://go.microsoft.com/fwlink/events.asp.
I resolved the issue by opening the map in my text editor and replacing all instances of "\obj\Debug\" with "\obj\Release\"